If you are using Super Socializer plugin for Social Login, follow the steps mentioned below to enable Facebook login at your WordPress website.

Steps To Enable Facebook Login

Navigate to Facebook Developers section and login to your Facebook account, if you are not logged in already. This should not be your business account.

If you are here (at Facebook Developer section) first time, you will require to “Register as a Developer” (If you have already done this, skip this step and move to step 3). Click “Register” button.Accept the privacy policyYou may be asked other details as in following pictureNext, you will be shown a messageAfter clicking Done, you will be redirected to the Apps page.
Click Create App button and navigate to step 4.

Hover MyApps and then click “Add a New App” link.

Specify the name of your app in Display Name option (You can enter whatever name you like, but it’s recommended to enter your website or company name in this field), specify your Contact Emailand click Create App ID button

Click Set Up in Facebook Login section

Select Web

Open your website homepage (at which you have installed the plugin) in browser, click the address bar so that website url gets highlighted, copy this url and paste it in Site URL option. Please make sure that this url includes http:// or https:// (for example: http://mywebsite.com or http://www.mywebsite.com), click Savebutton

Navigate to Facebook Login >Settings section from the left sidebar

Use the same url you used in step 7 above and paste it in Valid OAuth redirect URIs option. Please make sure that this url includes http:// or https:// (for example: http://mywebsite.com or http://www.mywebsite.com) and click Save Changes button

Navigate to Settings page from left sidebar

Specify your website domain (with and without www) in App Domains option. For example, if your website homepage url is www.mywebsite.com or mywebsite.com, you have to save mywebsite.com and www.mywebsite.comin this option.Note: If your website url has directory/folder after domain (For example- http://www.mywebsite.com/dir), then save domains without directory/folder appended to it (www.mywebsite.com and mywebsite.com) in above option.
Specify Privacy Policy URL.
Select Social Networks and Dating in Category option. Optionally, you can upload App Icon. This will be shown to users when they authorize your app on first Facebook Login.
Click Save Changes button.

Navigate to Dashboard page from left sidebar

Click the [?] after “This app is in development mode and can only be used by app admins, developers and testers”

Click No before “Your app is in development and unavailable to the public” and slide it to Yes